KR20020011407A - Methods and systems for error handling in radiocommunication systems employing pre-paging - Google Patents

Abstract

A method and system are described for handling errors associated with spare calls in a wireless communication network. If the wireless connection to the terminal is lost after the subscriber reserve call, the network can detect this event. Then, when a corresponding call forwarding message is received, the network may recall the terminal and reallocate radio resources if the terminal is available. Additionally, a guard timer can be started when the radio resource is initially allocated. If a call forwarding message is received before the timer expires, the radio resource may be released to prevent waste of this resource in the event that the call forwarding message is lost in the network.

Description

METHODS AND SYSTEMS FOR ERROR HANDLING IN RADIOCOMMUNICATION SYSTEMS EMPLOYING PRE-PAGING

<Related / Previous Application>

This application claims the priority of US Provisional Application 60 / 133,688, "Gateway Location Register and Pre-Paging In the Universal Mobile Telecommunication System," filed May 10, 1999. The entire contents of which are incorporated herein by reference.

The wireless communications industry has made significant strides in commerce in the United States and elsewhere in the world. Growth in major metropolitan areas has exceeded expectations and far exceeds system capacity. If this trend continues, the effects of this industry's growth will soon reach the smallest market. In order to meet the demand for this increasing capacity, as well as to maintain high quality services and to prevent price increases, innovative solutions are required.

One technique commonly used in such wireless communication systems is a technique called paging. Calling is a process that enables a wireless communication system to locate a terminal for which a communication (eg, incoming call attempt, message delivery, etc.) is requested. For example, in many wireless communication systems, an idle mobile station (i.e., a mobile station that is not assigned a traffic channel) will listen to a call channel for a call message with an address assigned to it. The listening process may be performed periodically to save battery power by allowing the terminal to reduce power between reception periods. However, when a terminal receives a call with an address assigned to it, the terminal acknowledges the call and begins a process for establishing a connection between the terminal and the wireless communication system. This process provides routing information for the called terminal to the wireless communication system so that messages can be sent to the terminal's current location.

An example of a conventional calling technique is now described with respect to a GSM wireless communication system. Among the techniques for the GSM wireless communication system, the calling technique is at least partly disclosed in a standard document called GSM TS 09.02 (ETSI ETS 300 974), the contents of which are incorporated herein by reference. In this document, the Mobile Application Part (MAP) for the GSM network handles the signaling interaction between the visiting PLMN (VPLMN) and the home PLMN (HPLMN) when a connection with the terminal is to be established. The prior art for this is disclosed.

1A shows a conventional process for establishing a connection with the terminal 5. Here, the gateway mobile switching center (GMSC) 10 receives an initial address message (IAM) to reach a particular mobile subscriber (message 1). GMSC 10 then requests the roaming number of terminal 5 from home location register (HLR) 20. As a result, the GMSC 10 can designate an MSC (not shown) supporting wireless communication with the current terminal 5 in the VPLMN. The GMSC 10 sends a Send Routing Information (SRI) message (message 2) to the HPLMN that owns the subscriber associated with the terminal 5, i.e., to the HLR 20 of the terminal's home system. Achieve this. Note that the physical relationship between the nodes of FIG. 1A is conceptually illustrated, and implementation methods may vary physically. For example, the GMSC may be mounted in the HPLMN or may be mounted in the originating PLMN.

When the HLR 20 receives an SRI message from the GMSC 10 (GMSC is not necessarily inside the HPLMN), the HLR 20 is a visited mobile switching center / service serving the area where the terminal 5 is located. The roaming number will be requested from the Visit Location Register (VMSC / VLR) 30. In this example, the VMSC and VLR are shown as joining nodes, but it should be noted that they may be separate nodes. In addition, throughout this specification, these nodes will be referred to individually. The request for a roaming number can be accomplished, for example, by sending a Provide Roaming Number (PRN) to the VMSC / VLR 30 (message 3). The VMSC / VLR 30 in the VPLMN provides a roaming number, which is passed through the HLR 20 to the GMSC 10 using the PRN & SRI message. The GMSC 10 then sends an IAM (message 4). ) To the VMSC / VLR 30.

After the IAM (Message 4) has been received by the VMSC / VLR 30, a number of internal messages occur within the VMSC / VLR node (i.e., transfer of information about incoming calls, calls), and as a result the subscriber's terminal Will be called (message 5). After receiving the call confirmation notification from the terminal, a call channel may be established between the terminal and the serving base station (not shown) to establish a connection. FIG. 1B is a flow chart illustrating the procedure described above and shown in FIG. 1A. An important feature of the conventional calling technique is that the call of the terminal 5 does not occur until the VMSC / VLR receives the IAM message, as can be seen in this figure.

Recently, another method for handling a connection with a terminal has been considered. This method has been referred to as paging-before-routing or pre-paging. In a wireless communication system using a spare call, the VMSC / VLR waits for the roaming number (e.g. MSRN) from the HLR instead of waiting for the IAM to be delivered as in the case of the conventional calling technique described above. / VLR initiates the call of the subscriber terminal. In addition, the roaming number is not sent to the HLR until a call response from the subscriber station is received indicating that the terminal is currently available, which is different from the technique described above in which the VMSC / VLR returns the roaming number immediately upon receipt of a request from the HLR. Is the point.

This preliminary calling procedure has at least one important advantage compared to the conventional calling technique of FIGS. 1A and 1B. If the subscriber station does not answer the call, the call cannot be completed (which can happen very often) as in the case of the conventional GSM procedure described above, and switching and transmission between the GMSC 10 and the VMSC / VLR 30 Resources are not unnecessarily occupied. Therefore, the reserve call technique can use less switching and transmission resources in the incoming and outgoing network.

2A shows a conventional procedure associated with an exemplary reserve call to handle a connection. As shown in this figure, the GMSC 10 receives an Initial Address Message (IAM) to forward a call to the mobile terminal 5 (Message 1). GMSC 10 then sends an SRI to the HLR (message 2) to request the roaming number. The HLR will send a PRN (message 3) to request a roaming number from the VLR.

In this respect, the procedure shown in Fig. 2A is identical to the GSM procedure shown in Figs. 1A and 1B. However, before the VMSC / VLR 30 of the VPLMN provides a roaming number, the VMSC / VLR 30 will make a preliminary call to the terminal 5 (ie, to confirm the availability of the subscriber in its service area). Call the terminal even if the VMSC / VLR does not have an IAM message yet) (message 4). Only after a successful call to the subscriber, the VMSC / VLR 30 provides a roaming number that is passed to the GMSC 10 via the HLR 20 (i.e., in the PRN and SRI response). In addition, only after a successful preliminary call to the subscriber, a radio resource, for example a signaling channel for the mobile station for responding to the call request, and optionally a call channel to which the call can be connected, is assigned to the call. Then, after receiving the response to the SRI message, GMSC 10 may forward the IAM to VMSC / VLR 30 (Message 5). An information flow diagram for the procedure of FIG. 2A is shown in FIG. 2B.

The procedure shown in Figs. 2A and 2B reflects the preliminary calling feature in a normal state, i.e., all network nodes involved are normally processed. However, network failures can occur during the preliminary calling process and these failures will have a deleterious effect on wireless communication system performance. For example, consider a situation where the radio connection with the subscriber station 5 is lost after the terminal 5 is called and the roaming number is provided by the VMSC / VLR 30. Subsequently, when the IAM message arrives at the VMSC / VLR 30, the VMSC will not associate the IAM message with the terminal because the radio resource is released.

As another example of a network failure that may occur during a preliminary call, an IAM message sent by the GMSC 10 after the terminal 5 is called and the roaming number is provided by the VMSC / VLR 30 may be lost due to network congestion. Consider a situation that is lost during routing between 10) and VMSC / VLR 30. In this case, the radio resource remains allocated for the expected call even though the IAM message is lost in the network, and this situation reduces system capacity because the resource is unnecessarily occupied.

Thus, while also handling this type of failure or error in the network, the benefits of conventional preliminary calling techniques (eg, preventing the use of network resources to deliver IAM messages when the terminal is not available). It would be desirable to provide a preliminary calling technique in a wireless communication system that can enjoy.

The present invention relates to a calling technique in a wireless communication system, and more particularly to a technique for error handling in a wireless communication system using a reserve call.

1A is a signaling diagram of a conventional calling technique for establishing a connection with a terminal.

1B is an information flow diagram corresponding to the conventional calling technique shown in FIG. 1A.

2A is a signaling diagram of a preliminary calling technique for establishing a connection with a terminal that can utilize an embodiment of the present invention.

2B is an information flow diagram corresponding to the preliminary calling technique of FIG. 2A.

3 is a block diagram of an exemplary base station and mobile station that may be used to implement the present invention.

4 is a flow diagram illustrating a first exemplary embodiment of the present invention for handling the loss of allocated radio resources after a reserve call.

5 is a flowchart of an exemplary method according to the first exemplary embodiment.

6 is a flow diagram illustrating a second exemplary embodiment of the present invention for handling the loss of a call forwarding message after a preliminary call.

7 is a flowchart illustrating an example method according to the second example embodiment.

In accordance with an exemplary embodiment of the present invention, an error procedure has been developed by the Applicant to avoid problems that may occur when a subscriber of a VPLMN is preliminarily called.

For example, according to the first embodiment of the present invention, it solves the problem of the radio connection with the lost subscriber terminal after the preliminary call. According to this embodiment, the loss of the wireless connection is detected and recognized by the system. After receipt of a call delivery message, the terminal is called again and, if available, radio resources are allocated back to the terminal. Therefore, this second set of radio resources is established in association with the received call initiation message.

According to another embodiment of the present invention, while waiting for a lost IAM message, solves the problem that the radio resources continue to occupy the terminal after the call. According to this embodiment, the guard timer is started at the number allocated to the radio resources in response to the successful reserve call. If the guard timer times out before the call initiation message is received, the radio resource is released.

In the following description, specific details, such as specific circuits, circuit components, techniques, etc., are intended for a thorough understanding of the present invention and are not intended to be limiting. However, it will be apparent to one skilled in the art that the present invention may be practiced with other embodiments than the specific details. In other instances, detailed descriptions of well-known methods, devices, and circuits have been omitted so as not to obscure the description of the present invention.

The exemplary wireless communication system referred to herein has been described as being implemented in accordance with the GSM specification using a time division multiple access (TDMA) protocol in which communication between a base station and a mobile terminal is performed using multiple time slots. However, one of ordinary skill in the art will appreciate that the concepts disclosed herein are not limited to, but in accordance with other protocols including frequency division multiple access (FDMA), code division multiple access (CDMA), or hybrids of the aforementioned protocols. It will be appreciated that it can be used in a working system.

For illustration purposes, FIG. 3 shows a general example of a conventional cellular wireless communication system 100 in which the present invention may be implemented. The wireless communication system 100 includes a plurality of radio base stations (BSs) 30a-30n in which only one mobile station (MS) 5 communicates with a plurality of illustrated mobile terminals. The communication from the base station to the mobile station 5 is commonly referred to as downlink communication, and the communication from the mobile terminal to the base station is referred to as uplink communication.

Base stations 30a-30n are coupled to a mobile switching center (MSC) / visitor location register (VLR) 50. Among other tasks, the MSC / VLR 50 coordinates the activity of the base station, such as during handoff of a mobile station from one base station to another. On the other hand, the MSC / VLR may be connected to a public switched telephone network (not shown). Each base station 30a-30n will have a plurality of transceivers 35 that are used to transmit information on the RF carrier associated with the call and signaling channel. Each mobile station, such as mobile station 5, is a transceiver for communicating with the base station 30a via an air interface with various I / O devices, such as displays, speakers, microphones, keypads, etc., represented by block 20. (10) is provided.

When establishing a connection between the wireless communication system (shown in FIG. 3 as base station 30a) and the mobile station 5 using the preliminary calling technique according to the present invention, the various potential error conditions described above are solved. First, an exemplary embodiment of the present invention solves the problem associated with lost wireless connection with a subscriber terminal after a successful preliminary call as shown in FIGS. 4 and 5. First, in step 500, a call is initiated using, for example, the IAM, SRI and PRN signals described above. In this situation, call initiation refers to, for example, call forwarding or establishment reaching a cellular phone. Then, in step 502, the terminal is preliminarily called. As described above, after the mobile station 5 is preliminarily called, a first set of radio resources is allocated in step 504, for example, waiting for transmission of call setup information, which is a channel assignment message. A signaling channel is assigned, for example. If the MSC / VLR 30 receives an IAM message while the mobile station is in wireless connection with the system using the first set of radio resources (the “No” and “Yes” paths, respectively, in steps 506 and 508). ], A call can be established using this resource (step 510).

Alternatively, if the mobile station 5 moves out of range of the assigned base station 30a to transmit call establishment information to the mobile station 5 via the assigned signaling channel during the preliminary call processing, the system uses the first set of resources. You may not be able to listen.

If the wireless connection is lost, the MSC / VLR 50 acknowledges this event (eg, by setting a flag associated with the mobile station identification number in step 512) and, in step 514, is already in the call to be established. Release all allocated radio resources (e.g., signaling channels and call channels). This release of resources is indicated in Figure 4 by the break of a thick black line drawn vertically from the spare call block connecting the MS 5 and the MSC / VLR. When an IAM message associated with an already called subscriber arrives at the MSC / VLR [step 516], the MSC / VLR recognizes that the established radio connection with the terminal identified in the IAM message has been lost (eg, set of flags in memory). Using the state). Then, in step 518, a second call of the mobile station 5 is performed to ascertain the availability of the terminal in the MSC / VLR service area. If the subscriber is still available, a second set of radio resources (either equal to or not equal to the first set of radio resources) is allocated to support the call and the MSC / VLR sends an incoming IAM message to complete the call establishment process. Associate with a newly allocated radio resource.

Another problem associated with the conventional reserve call technique, namely, how to handle the loss of IAM messages in the network after the reserve call, is addressed by the exemplary embodiment of the invention shown in FIGS. 6 and 7. This problem has been discussed above and can be readily seen in the flow chart of FIG. 5 by noting the loop created by the “no” path of decision blocks 508 and 516. As before, the system initiates the call [step 700] and preliminarily calls the terminal [step 702]. After the preliminary call is successful, in step 704, the MSC / VLR receives the radio resource. (Eg, a signaling channel and optionally a call channel), then a guard timer is started at step 706. This guard timer must receive an indication that the GMSC was successful in preliminary calls. The resulting IAM message may have a countdown (or countup) time related to the time the MSC / VLR has to arrive at, for example, this period of time may be on the order of 20 ms, but one skilled in the art would have a certain amount of guard time. It will be appreciated that it may change.

After the guard timer is started, the MSC / VLR 30 will wait to receive the IAM message associated with the terminal with the allocated radio resource based on the successful reserve call as indicated in step 708. If received, the MSC / VLR will proceed as indicated in step 710 to set up the call. Otherwise, if the guard timer expires prior to receiving the IAM message (“Yes” path from decision block 712), the MSC / VLR will release the allocated resource at step 714. Initiating a guard timer in the VMSC in order to confirm timely release of radio resources when the network fails as described above gives a number of advantages. For example, a UMTS network that uses the reserve call feature may provide robust capability even in the event of a failure during the reserve call procedure.

The exemplary embodiments described above are intended to illustrate in all respects, not to limit, the invention. Therefore, many changes are possible in the detailed implementation that can be derived from the description contained herein by one of ordinary skill in the art. For example, the embodiments of FIGS. 5 and 7 can be easily combined. All such variations and modifications are considered to be within the spirit and scope of the invention as defined by the appended claims.

Claims (11)

A method for communicating with a terminal in a wireless communication system, a) initiating a call to the terminal; b) pre-paging the terminal to determine if the terminal is available, c) allocating a first set of radio resources for the call if the terminal is available; d) detecting a loss of wireless connection with the terminal; e) delivering a call delivery message to a first node that has a service area in which the terminal is located; f) calling the terminal a second time after the call forwarding message is received; g) allocating a second radio resource to the call if it is determined that the terminal is available to process the call in response to the call step f). Communication method comprising a. 2. The method of claim 1, wherein allocating the first and second sets of radio resources comprises allocating a signaling channel to the terminal. 2. The method of claim 1, wherein allocating the first and second sets of radio resources comprises allocating a call channel to the terminal. 2. The method of claim 1, further comprising storing an indicator of loss of wireless connectivity at the first node. 2. The method of claim 1, further comprising providing a roaming number for the terminal to a second node generating the call forwarding message after determining that the terminal is available in response to the preliminary calling step b). . 6. The method of claim 5 wherein the first node is a visited mobile switching center (VMSC) and the second node is a gateway mobile switching center (GMSC). A method for establishing a connection with a terminal in a wireless communication system, a) precalling the terminal to determine availability of the terminal, b) selectively allocating a first radio channel to the terminal based on a result of the preliminary calling step; c) calling the terminal a second time due to the detected loss of the allocated radio resource, d) assigning a second radio channel to the call if it is determined that the terminal is available to process the call in response to the call step f). How to include. A method for communicating with a terminal in a wireless communication system, a) initiating a call to the terminal; b) precalling the terminal to determine if the terminal is available; c) allocating radio resources to the terminal if the terminal is available; d) starting a guard timer, e) transmitting a call start signal to a node supporting communication with the terminal, f) determining if the guard timer has expired before the call initiation signal is received by the node, g) releasing the already allocated radio resource if it is determined that the call initiation signal has not been received before the guard timer expires. Communication method comprising a. 9. The method of claim 8 wherein the guard timer expires after 20 milliseconds. A resource processing method associated with a terminal call in a wireless communication system, a) allocating radio resources to the terminal after a successful reserve call; b) starting the guard timer in response to step a), c) releasing the radio resource if a call forwarding message is not received before the guard timer expires Communication method comprising a. The method of claim 10, Pre-calling the terminal; Transmitting the roaming number for the terminal to the node generating the call forwarding message after the terminal determines whether it is available in response to the preliminary calling step.